In appendiceal cancers, RB1 gene mutations are reported in some isolated cases of appendiceal cancers without further specification, low-grade appendiceal mucinous neoplasms [15,30], mucinous adenocarcinomas of the appendix, and appendiceal goblet cell adenocarcinoma, without being defined for them. The gene discussed is RB1; the disease is mucinous adenocarcinoma of the appendix.